Blog | G5 Cyber Security

Fix ARP Spoofing Issues

G5 Cyber Security

TL;DR

ARP spoofing not working? It’s usually down to a few common things: your network card settings, other security software interfering, or the target already being protected. This guide walks you through checking these and getting it running.

Troubleshooting ARP Spoofing Problems

  1. Check Your Network Interface
    • ARP spoofing needs your network card to be in ‘promiscuous mode’ – meaning it listens to *all* traffic, not just what’s addressed to it.
    • On Linux, use 
      ifconfig eth0 promisc

      (replace eth0 with your interface name). If it says ‘promisc on’, you’re good. If not, try 

      sudo ifconfig eth0 promisc on

      .

    • On Windows, this is usually enabled by default but can be checked in Network Connections properties (advanced settings) – look for ‘Promiscuous Mode’.
  2. Disable Conflicting Software
    • Antivirus and firewalls often block ARP spoofing. Temporarily disable them to test if they’re the problem. Remember to re-enable them afterwards!
    • Some network monitoring tools also interfere. Close any running programs like Wireshark or similar packet sniffers.
  3. Verify Target IP Address and MAC Address
    • Make sure you have the correct IP address for your target machine. Use 
      ping target_ip

      to confirm it’s reachable.

    • Get the target’s current MAC address using 
      arp -a target_ip

      . You need this to build the spoofing packets correctly.

  4. ARP Cache Poisoning Protection
    • Many modern operating systems and network devices use ARP cache poisoning protection (e.g., Dynamic ARP Inspection). This actively prevents ARP spoofing attacks.
    • If the target has this enabled, your simple spoofing attempts won’t work. You might need more advanced techniques or a different attack vector. There’s no easy fix on the target side if it’s intentionally protected.
  5. Check Your Spoofing Tool and Script
    • Ensure your ARP spoofing tool (e.g., Ettercap, arpspoof) is up-to-date. Older versions might have bugs or compatibility issues.
    • Double-check the syntax of any custom scripts you’re using. A small error can prevent it from working correctly.
  6. Network Topology and Switches
    • ARP spoofing works best on a simple network (e.g., directly connected devices). Managed switches with port security features can block ARP requests from unauthorized MAC addresses.
    • If you’re using a switch, check its configuration to see if any security policies are in place that might be interfering.
  7. Use a Different Tool
    • Try a different ARP spoofing tool to rule out issues with the specific program you’re using. Ettercap is a popular and reliable option.

If none of these steps work, the target network might have more sophisticated cyber security measures in place that are actively preventing ARP spoofing.

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